A216543 - OEIS

%I #23 May 11 2024 16:27:36

%S 3,1,4,1,5,7,2,6,5,3,5,8,9,7,9,5,2,3,8,4,6,2,6,4,2,3,8,3,2,7,9,5,0,4,

%T 1,0,4,1,9,7,1,6,6,6,2,9,3,7,5,1,1,5,9,2,5,1,7,4,8,9,0,5,3,7,0,0,8,2,

%U 1,5,1,2,8,2,4,4,3,3,0,6,9,6,2,4,7,1,3,2,4,1,8,1,1,0,1,9,4,7,0,5,3,7,6,8,7,2,6,5,4,8,5,0,1,8,7,4,0,9,6,5,0,1,2,3,8

%N Decimal expansion of 4*Sum_{k=1..50000} (-1)^(k-1)/(2k-1).

%C An approximation to Pi.

%H J. M. Borwein, P. B. Borwein, and K. Dilcher, <a href="http://www.jstor.org/stable/2324715">Pi, Euler numbers and asymptotic expansions</a>, Amer. Math. Monthly, 96 (1989), 681-687.

%H J. M. Borwein and R. M. Corless, <a href="http://www.cecm.sfu.ca/~jborwein/sloane/sloane.html">Review of "An Encyclopedia of Integer Sequences" by N. J. A. Sloane and Simon Plouffe</a>, SIAM Review, 38 (1996), 333-337.

%e 3.14157265358979523846264238327950410419716662937511592517489...

%t First[RealDigits[4*Sum[(-1)^(k-1)/(2*k-1), {k, 50000}], 10, 100]] (* _Paolo Xausa_, May 11 2024 *)

%Y Cf. A000796, A216542, A013706, A216543, A216544, A216545, A013705, A216546, A216547, A216548.

%Y Cf. also A195793.

%K nonn,cons

%O 1,1

%A _N. J. A. Sloane_, Sep 08 2012